I mean, honking a car horn at any animal would probably scare it.

That's not possible. Not because I'm not able to check for mobs, but because mobs do their scaring based on other mobs, not a bit or state set in their code. e.g. Creepers only run if there's an ocelot nearby. Unless I override a large portion of MC's code, I can't get mobs to run in fear of a semi truck, so you'll have to settle for just running down zombies like every other survival player.